Pascal/Turbo Pascal - Como hago para que no se me logge cuando cambio de posicion el cuadrito!..

program linea;

uses

wincrt, graph;

var

drive, modo : integer;

x,y:word;

move:char;

begin

drive := detect;

initgraph(drive, modo,'c:\fpc'); {ponlo a tu direccion}

x:=500;

y:=510;

repeat

rectangle(x,500,y,510);

move:=readkey;

if move='M' then

if (x<1010) and (y<1020) then

	begin

	x:=x+10;

	y:=y+10;

	rectangle(x,500,y,510);

	cleardevice;

	end;

if move='K' then

if (x>10) and (y>20) then

	begin

	x:=x-10;

	y:=y-10;

	rectangle(x,500,y,510);

	cleardevice;

	end;

until move='S';

end.

{Mira esto te puede ayudar }

program muevepaleta;

 uses

    wincrt, graph;

 type

    paleta = array[0..2040] of byte;

  var

    pale : paleta;

    x, y, xp, yp : integer;

    drive, modo : integer;

    pulsada : word;

  function tecla : word;

  var

    tec : char;

  begin

     tec := readkey;

     if tec = #0 then

     tecla := word(ord(readkey)) shl 8

   else

     tecla := ord(tec);

  end;

  procedure tomapaleta(x,y,xx,yy : integer; tm : char);

  var

    dig, t1, t2 : integer;

  begin

      if upcase(tm) = 'C' then

      begin

      dig := 0;

      for t1 := x to xx do

        for t2 := y to yy do

        begin

           pale[dig] := getpixel(t1,t2);

           dig := dig + 1;

        end;

      end;

      if upcase(tm) = 'D' then

      begin

         dig := 0;

          for t1 := x to xx do

           for t2 := y to yy do

           begin

              putpixel(t1,t2,pale[dig]);

              dig := dig + 1;

           end;

       end;

  end;

  procedure iniciografico;

  begin

      drive := detect;

      initgraph(drive,modo,'c:\tp\bgi');

      if graphresult <> 0 then

      halt(1)

    else

       begin

          clearviewport;

       end;

  end;

  begin

     iniciografico;

     x := 1;

     y := getmaxy - 10;

     outtextxy(80,8,'Pulsando [ESC]=Termina, Flechas=[Derecha] y ' +

                                              '[Izquierda]=Mueven');

     line(1,y + 4,getmaxx - 5,y + 4);

   repeat

     tomapaleta(x,y,x + 20,y + 8,'c');

     rectangle(x,y,x + 20,y + 8);

     pulsada := tecla;

     tomapaleta(x,y,x + 20,y + 8,'d');

     if pulsada = 19712 then

     begin

     x := x + 25;

     if x > getmaxx - 25 then

     x := getmaxx - 25;

     end;

     if pulsada = 19200 then

     begin

     x := x - 25;

     if x < 1 then

     x := 1;

     end;

   until pulsada = 27;

     closegraph;

  end.